Little GEM

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The mosfet operation (depletion mode) was discussed in mine other thread. It is just CCS and it gives combination of CCS and bootstrap VAS, and I never saw anything similar used before.
If you like to build this amp here is last layout in pdf. In my prototype I used older layout, so it needs check and you can change mosfet from TO220 to TO92 type.
Damir

I've found some layout error in that PCB, Ian will have gerbers for new layout if someone interested.
Damir
 
I was looking to picked details around B-AKSA and stumble here to little GEM.
Interess is waked up- not fully understand, but i know Damir is an old Fox with many
knowledge.
One pair boards for a build would be enough. How to get?

regards
 
Congratulations, you're design is very good amplifier. This amp can do a bit better. Look at R5L1. This circuit will add depth NFB.

Thank you for your comment and suggestion. I simulated it with added RL between LP emitters and I've got some marginal THD20k improvement, but with some Phase Margin loss. I tried to optimize RL but still not to big difference. To get better result, I suppose I have to optimize whole LP and it's not worth the effort as distortion is already very low.
 
tPD = Gain*tPD(Gain=+1)

Propagation Delay, nS and Unity Gain Frequensy (UGF), MHz for some operational amplifiers:
LM6172 – 1,0 (100); THS4041 - 1,7 (89); LT1363 (64) - 2,0 (70); EL2044 – 2,5 (38); AD817 - 3,0 (50); AD843 – 4,6 (34); LM837 - 7,0 (25); AD744 - 8,0 (13); OPA627 - 10,0 (16); OPA2132 - 13,9 (8,7); NE5532 – 16,2 (9); TL072 – 53,6 (2,7)
 
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